A meltdown may be occurring at one of the reactors at an earthquake-damaged nuclear power plant in northeast Japan, a government official told CNN Sunday morning Japan time.

"There is a possibility, we see the possibility of a meltdown," said Toshihiro Bannai, director of the international affairs office of Japan's Nuclear and Industrial Safety, in a telephone interview with CNN from the agency's Tokyo headquarters. "At this point, we have still not confirmed that there is an actual meltdown, but there is a possibility."

Bannai said engineers have been unable to get close enough to the reactor's core to know what's going on, and that he based his conclusion on radioactive cesium and iodine measured in the air near the plant Saturday night.